Thomas j



(No Model.)

' T. J. PERRIN.

UiRGUIT FOR TELEPHONE EXUHANGES. V No. 315,334. Patented Apr. 7, 1885.

WITNESSES Q, W his 4 2527121698 T72 omas J P617272 N. PETERS Phalo-Lflhographer. Washington. 0, c

UNITED STATES PATENT OF ICE. 1

THOMAS J. PEBRIN, OF BROOKLYN, NEW YORK, ASSIGNOR To CHARLES r.

HUNTINGTON, or GREENVILLE, MISSISSIPBL CIRCUIT FOR TELEPHONE-EXCHANGES. v

SPECIFICATION forming part of Letters Patent No. 315,334, dated April 7, 1885 Application filed November 4. 1884. (No model.)

To aZZ whom it may concern.-

Be it known that I, THOMAS J. PERRIN, of Brooklyn, Kings county, New York, have invented certain new and useful Improvements in Circuits for Telephone-Exchanges, of which the following is a specification.

The object of my invention is to provide a practical andefficient means by which a single main battery located at the central ofiice may be used by the subscribers calling in that class of telephone-exchange systems in which independent calling and talking circuits are used.

The accompanying drawing is a diagram I 5 view illustrating an annunciator at a centraloffice and the apparatus of a subscriber.

By means of my invention I dispense with the usual magneto call-bell, which, although adopted generally by existing telephone-companics, has a great number of serious defects,

as is well knownby those who have had experience.

By employing a single battery of suitable power at'the central office much trouble and 2 5 annoyance arising from the imperfections of the magneto calls at the several subscribers stations are obviated.' By means of a battery more loud and distinct signals may be made both in calling the central office and in call- 0 ing the subscribers. The arrangement is also useful in case the ordinary snbscribers line which leads to his annunciator becomes grounded or otherwise defective, as any subscriber may then indicate at the central office 3 5 that his particular line is in trouble. 7

Referring, now, to the accompanying drawing, MB represents a main battery at the central oilice, from which two lines from the same pole of the battery run to the various subscri- 0 bers stations. These lines constitute the calling-circuit, and are indicated by dotted lines. They will be joined at the last subscribers station in the loop, so. that there is a continuous metallic circuit from the pole of the bat- 5 tery to the various subscribers stations and back to the same pole of the battery. The line is preferably arranged in this way to provide against liability of its getting out of order. If one leg of the loop is broken, the subscrib- 5'0 ers can call through the other side, as described below. This calling-line ismarked cl. In addition to this calling-circuit there aresubscribers lines. Such a line isshown in the drawing, and runs from the lower contact, 8, of a switch, S, at the subscribers station to the central oflicc andthrough the annnnciator-magnet, armature, and drop to earth. This line is lettered sl. At the central office the ordinary operators instruments are connected with the upper contact-stop,. a, of the the annunciator-arm'ature, as clearly shown. The annunciator-drop is permanently connected with the earth, and whenever it falls makes contact with a stop, I), electrically connected with the same pole of the. battery as the calling-loop,so that when the annunciatordrop falls the entire battery is grounded. At the central oiiice O is an ordinary gong-bell placed in the calling-circuit. At the subscribers station D is also an ordinary gong 7o bell,w-hioh is connected with the under plate, 15, of a switch, 1, and is grounded through the wire d. The subscriberstelephone is provided with a wide-faced switch-plug,U,whioh plugs simultaneously to both switches Tand S. Wheneyer, therefore, the plug is inserted in these switches to suspend the telephone, the main line, entering the subscribers station at the plate 8 of the switch S, crosses through the switch-plug U to the under plate,

83. t, of the switch T; thence to gong-bell and earth. The upper face of the switch-plug U 9 then to plate .9, upper plate of switch S, sec

ondary of induction-coil,\and telephone to matter of Letters Patent No. 309,357, granted to me December 16, 1884, and no claim is therefore made to it in this case. The arrangement is here shown as merely illustrating one form of apparatus for a subscribers station. A key, K, is placed in the subscribersline 81 at the subscribers station, and is adapted to make contact with a contact-point, 7c, connected with one side of the calling-circuit cl. Normally, the subscribers telephone is of course suspended in the switches T S. It, now, he desires to call the central office, he presses the key K against the button k. This completes a divided circuit from the main battery MB at the central office, the current from which divides at the key K, part of it passing to switch-plate s, telephone-hook-U, switch-plate t, and gong-bell to ground, and the other by the subscriber s line sl through the annunciator-coil A, its armature, and drop to ground. If, therefore, the operator is not otherwise engaged, and is ready to make the connection, as will presently be described, the annunciator-drop will fall at the same time that the ringing of the subscribers bell indicates that his call has been received. The annunciatorarmature will throw the operators instruments into the line, so that the subscriber can communicate with him. At the same time the drop of the annunciator, by falling upon the contact-button b, grounds the main battery MB. Should any other subscriber now call in like manner, while the operator is engaged with the subscriber who first called, he would get no current from the main battery MB, because the entire current would be shunted through the annunciator-drop. Such subscriber s bell would therefore not ring, and he would know that the operator was engaged. As soon as the operator has attended to the subscriber first calling, as above described, the armature drop is put up and the operator is ready to attend to other calls. At the central office the operator calls any subscriber by plugging to his terminal and touching the plug on the other end of the cord to a general calling-battery plate or bar-a manner of operation common and well understood. The effect of sending such a signal at the central office is, of course, to let the annunciator-drop fall, thus grounding the main battery MB, so that the operator cannot be interrupted until he has finished making the connection he is engaged on.

One great advantage of the organization above described is, that if the subscriber s line 81 becomes grounded he may, by manipulating the key K, ring the gong O at the central office, thus indicating to the operator that that particular line is in trouble and needs examination. The circuit in this case will be from the main battery MB, by way of either leg of the loop of the call-circuit 01, to the button It, key K, and ground through the subscribers gong. Suppose the subscriber was No. 23. He would first firmly depress the key Ktwice, then pause, and then depress it three times. This operation could be repeated several times to insure the attention of the operator at the central oifice, who would understand that the subscribers line 31 was out of order. The liability of the calling-circuit being out of order at the same time that the subscribers circuit is is exceedingly remote, because the interruption of the calling-circuit on either side of the subscribers station will not prevent him sending in such a signal, and the occurrence of defects on both sides of the subscriber at the same time will best-ill more unlikely to occur.

I have merely diagrammatically illustrated and shown the connections of one subscriber with the central office; but the multiplication of stations is not necessary, as they all will work'upon exactly the same principle, and the two-wire system of telephone-exchanges is generally well understood by those skilled in this art.

I claim as my invention- 1. The combination of the general callingcircuit, the general calling-battery located at the central office, the subscribers line, a calling-key at the subscribers station connected in the subscribers line, its contact connected with the calling-circuit, and the subscribers annunciator at the central office.

2. The combination of the general callingcircuit, the calling-battery therein at the central office, the subscribersline, the key in the subscribers line, its stop connected in the calling-circuit, the subscribers annunciator at the central office, the annunciator-drop permanently connected with the earth, and the stop of the annunciator connected with the pole of the calling-battery.

3. The combination of the general callingcircuit, the calling-battery therein at the central office, the subscribers line, a key at the subscribers station connected in the subscribers line, its stop connected with the callingcircuit, agong-bell at the subscribers station, and the subscribers annunciator at the central ofiice.

4. The combination of a general callingcircuit, the battery and gong-bell therein at the central office, a key at the subscribers station connected in the subscribers line, and its stop connected with the calling-circuit.

5. In a telephone-exchange system, the combination of subscribers apparatus at the subscribers station, the subscriber s line, a general calling-circuit, a general calling-battery therein at the central office, and short-circuiting devices which ground the calling-battery at the central office when a subscriber calls.

In testimony whereof I have hereunto subscribed my name.

THOMAS J. PERRIN.

\Vitnesses:

J AS. PosEY, W. J. OLINE. 

